Study On Screening And Effect Of Cadmium Passivation Material In Soil Of Potato Production Area In Guizhou

The problem of Cd pollution caused by long-term soil zinc smelting and other human activities and high soil Cd background values has always been a prominent environmental problem in Weining County,Guizhou Province,which would cause agricultural pollution.This work aimed at comparing the passivation effect of different materials for the Cd in the soil and Screen out passivation materials suitable for the local area.For this purpose,we conducted a pot experiment to evaluate the effectiveness of five inorganic materials(Lime,Calcite,Hydroxyapatite,Bentonite,Sepiolite),three organic materials(Cow manure,Corn biochar),and two phosphate solubilizing bacteria(Bacillus megaterium,Bacillus glaci)in immobilizing Cd in soils,and Inhibiting Cd in potato.The pot experiment was mainly based on the yellow-brown soil in Weining County and two potato varieties(Qingshu 9 and Weiyu 5).The main results are as follows:(1)The soil in the potato production area is acidic.The comprehensive pollution index of heavy metals in the soil is at a severe pollution level and the individual potential ecological risk index of Cd in the soil is at a high to high-risk level.The soil of the potato production area has serious heavy metal pollution,and Cd is the most important pollution factor.(2)Applying Calcite,apatite,lime to soil increased the pH value of soil,applying Cow manure,Corn biochar increased the soil fertility.At the same time,applying different passivation materials would affect the composition and diversity of microorganisms in the soil.The microbial characteristics of the soil would also vary depending on the potato varieties.(3)Applying Calcite,apatite,lime to soil could promote the conversion of Cd in the soil into the stable chemical form.This further reduces the bioavailability of Cd in the soil.(4)By affecting the availability of Cd in the soil and the ability of potatoes to transport Cd,calcite,apatite,lime and corn biochar could effectively reduce the accumulation of Cd in the soil by potato tubers.The above materials mainly reduced the Cd accumulation capacity of potato tubers by inhibiting the absorption of Cd in various parts of the potato.(5)At last,Correlation analysis results show that the pH was the main factor of influence the reduction of the bioavailability of Cd in the soil.The availability of Cd in the soil is significantly negatively correlated with pH.Besides,the content of exchangeable-Cd and pH were the main factors affecting the Cd accumulation in potato tubers,and the relative impacts were 34.66% and 18.66% respectively.The availability of Cd in soil and the ability of potato tubers to accumulate Cd is also distinguished according to the relative abundance of parts of bacteria and fungi.In summary,four passivation materials,such as calcite,apatite,lime and corn biochar,were selected for remediation of soil cadmium pollution in the area affected by soil zinc smelting in northwestern Guizhou.Among them,calcite,apatite,and lime could effectively reduce the content of bioavailable cadmium and DTPA-Cd in contaminated soil,and reduced the absorption of Cd by potato roots and stems.Although the application of corn biochar did not significantly affect the availability of cadmium in the soil,it significantly reduced the cadmium accumulation in potato tubers.The changes in soil physical and chemical properties,texture and microbial composition caused by the application of different passivation materials may be an important reason for this phenomenon.